Two years after the March 11th tsunami in Japan that triggered the Nuclear disaster at the Fukushima power plant, there are still just over 300 thousand people who have not been able to return to their homes due to high radiation levels. The government has decided that radiation levels must be below 1 micro sieverts/hour (=5mSv/year, see here for what this means) before children can return to school in the area (adults may return to their home at 1.9micro-sieverts/hour, 10mSv/year) and there is a building-by-building clean-up effort that is going on to try and get the radiation levels down to the required levels.
The radiation levels are being measured from manned helicopters flying at approximately 300m but the issue is that the ground level where people actually live can only be estimated roughly from the air. To get the more accurate "human level" readings the government is relying on mobile surveying trucks or individuals wearing protective clothing but there has also been some limited use of UAVs.
In particular the very top image was taken at the Yamakiya elementary school (40km from the plant) using the Chiba University's MiniSurveyor hexacopter outfitted with a geiger counter. The readings were performed twice, once back in August 2012 and then again in December.
What you can see is that over the 4 months that significant portions of the school ground has returned to near natural levels and the part of the ground that was high radiation (2 ~ 3 micro-sieverts/hour) has mostly fallen to 1~2 micro-sieverts/hour. This area, by the way, is where the top few cm of earth from the school playground was removed and placed in the middle of the ground and covered by a plastic sheet.
During this test an EBA Japan Hyper-spectral camera was also used (although, in fact it was mounted on a manned helicopter mostly because it weighs 2kg and the mini-surveyor was perhaps unable to lift that weight for an extended period). These sorts of cameras can produce an image broken down into hundreds of bands of bands of light which can be used to determine what surface the radiation has fallen on. This is important because the level of radiation remaining at a site is greatly determined by the surface. For example it has been found that different types of trees retain radiation differently. A cedar will retain 50% of the radiation within it's leaves while an oak will only retain 20% (the rest falls to the ground).
After the clean-up is done, having a UAV capable of travelling over all the various different surfaces and verifying the success of the effort is another good use that's been put forward.
The Mini-surveyor was developed under the guidance of Professor Nonami (who wrote this book). It costs about about $15k each including a fancy simulator for learning how to use it. It apparently uses a "physical model" instead of PID controllers for attitude control. You can see a video of it flying here.
Comments
@hotel,
I know the government is actively looking for UAVs to map the area directly around the plant and even within the plant. If we're lucky it may even be an APM or PX4 that is involved. I suspect (and this is only a guess) if that's successful it might expand into something bigger, like a mapping of the surrounding cities.
I haven't heard anything direct re this though, it's based on what I've heard from some of the Japan based UAV people I know.
Hi Randy,
Is there any effort towards doing a fairly complete ground level mapping with small UAV(s) in the Fukushima area so that the contaminated land can be triaged and decontaminated/used based on radiation intensity maps??
Thanks, glad you like it. I follow their work and I'm on the executive committee of the group of companies that tries to help their progress but, unlike with arducopter, I don't my hands dirty with their actual product development. I think in general Japan is far behind the states but they have a real advantage (for the moment at least) when it comes to agriculture because the yamaha r-max has already blazed the trail for UAV use 10 years ago.
very nice video. Thanks for sharing! Are you by any chance affiliated with the lab? It is so hard to follow the work done in Japan...
Aha! forgot to upload the video that i spent so much time editing!
I have seen some work on all of these topics from other groups. Have you uploaded the video?
Awesome. Thank you!
@Mortiz,
It was based on a power point put together by EBAJapan and presented at a meeting of the "mini-surveyor consortium". As far as I know they haven't published exactly what was in the power point but some of it can be seen here. Some more of it can be seen on pg7 here.
There's actually some more interesting things going on in this group including a crop sprayer (for small japanese plots), automatic battery replacement system and a fixed line power source. I hope to upload a video about those in just over a week.
This is a very interesting article. It looks like these are figures out of a paper or a presentation. Do you happen to have a link to the source? Thank you!
@John,
I didn't actually catch that in the video but I don't think it can fly for 30min. Here's another page that has more about the different variations of the mini-surveyor and says they fly for 15min (which is pretty normal for a hexacopter these days). They've started moving towards using frames, batteries, etc from an RC supplier here in Japan called EnRoute who also sells the APM actually. I think their real specialty is they use this "physical" model instead of PIDs which means that they have very good attitude control for the frame they've been designed for. It takes more time to set-up the model for each frame type though I think.
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